Pump Selection Guide

Selecting The Right Pump Ten Commandments Of Pumping Tips For The Successful Operation Of Sump Pumps Tips for the Proper Selection Of Seals Used In Horizontal Pumps

The selection of the proper pump for a particular application is dependent upon a number of factors, including, but not limited to, the following material compatibility, pump size and type, pump speed and horsepower. Here are som guidelines to help you make the right choice.

Material Compatibility

Materials must be compatible withthe fluids to be pumped. Most plating solutions and many chemicals are corrosive, so pump materials must resist chemical attack. Corrosion-resistant chlorinated polyvinyl (CPVC) pumps are made in many sizes to handle a variety of pressure ranges and flow rates. CPVC withstands temperatures to 200ºF and somewhat higher at low pressures.

Polypropylene is suitable, but not as versatile as CPVC. Polyethylene, PVDF, Ryton®, Noryl® and PTFE are also available for specific solutions. Corrosion-resistant alloys are also available. Materioal used for seals and gaskets must be considered.

Pump Selection

Most pumps are of horizontal design. They are available in many flow rate / pressure combinations with either direct drive or seal-less magnetic-coupling. Which to choose? It depends on use conditions.

A direct drive pump requires careful seal selection to minimize wear and failure. Mechanical seals provide precision fit, are self-adjusting and are available water or product flushed. A closed-loop, double water flushed seal system also can be used when an external source of water is not available, or if theseal is to be self-contained.

Vertical pumps must have their drive motors mounted at the process tank. Fumes and mist from a plating bath or other corrosive process soultion can be a problem, so protect the motor if necessary. Vertical pumps are often used to pump waste solution from sumps.

Drum pumps are narrow enough to self-prime liquids through the bung opening. To add chemical for pH control or to add platign brightener, use a diaphragm or piston type metering pump. such pumps could be operated on timers or amp-hour meters.

Why speed and HP?

Pump sizing is largely a matter of determining the desired pressure and flow rate. Centrifugal pumps are avaialble with motor speeds of 1725 or 3450 RPM. The lower speed pump has half the flow, one-fourth the pressure and requires one-eigth the horsepower of the higher RPM model.

Pump ratings are based on moving liquid with a specific gravity of 1.0. For fluids with a specific gravity greater than 1.0, the required pump / motor horsepower of a direct drive pump can be determined by identifying the desired flow / pressure point on a performance curve and multiplying the indicated horsepower by the specific gravity of the fluid.

Many magnetic-coupled pumps are built with magnets capable of handling fluids with a specific gravity greater than 1.0. Care must be taken not to select a pump whose rating isn't adequate to handle the specific gravity of the fluid or th pump will lose synchronization and fail to pump. On some magnetic-coupled pumps, the impeller can be trimmed to pump higher specific gravity liquids.

In any match-up of pump and motor, make sure the piping is adequate. Piping too narrow can starve the pump and ruin efficiency.

Problems can abound such as:

Click to see the Ten Commandments of Pumping

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